1. Field of the Invention
The present invention relates to an optical disk drive capable of allocating, if a recording area on an optical disk medium includes a defective sector, a spare area for alternate-recording of the defective sector to another area on the medium, and it relates to a method for allocating a spare area on an optical disk medium.
2. Description of the Related Art
If rewritable optical disk media or write-once read-many optical disk media, including CD-R/RW, DVD±R/RW, and DVD-RAM, are each repeatedly used, a defect may occur in part of the optical disk medium. This is a defect caused by damage or a flaw of a medium, adhesion of fingerprints or a stain, aging of a recording film, or the like. Even if data is written to this defective part, the data cannot be successfully read out. It is difficult to prevent such a defect from occurring over the whole disk surface. For this reason, a defect management method is generally adopted. In this method, instead of writing data to a defective sector in which a defect has occurred, alternate recording for the defective sector is performed in a spare area that is allocated on the same optical disk.
At the time of initializing a format of an optical disk, an area having a fixed size (capacity) is usually allocated as the spare area. Because the spare area uses part of a user-data recording area, there is a limit of the size of the spare area that can be allocated. On the other hand, if the spare area is extended, an area to which a user can write data is decreased.
U.S. Pat. No. 6,469,978 discloses the technology for allocating a spare area whose size is variable. In the technology, application allows the size of a spare area to be changed so that the spare area can be properly allocated in response to frequency of accesses by users and the severity of data to be written.